Sound transmission and reproduction



Sept. 18, 1956 l H, M, SCHUMANN 2,763,333

SOUND TRANSMISSION AND REPRODUCTION Filed OCT.. 5, 1951 United StatesPatent O SUND TRANSMISSION AND REPRGDUCTION Hans Maassen Schumann,Philadelphia, Pa.; Josephine Mason Petts, executrix of said Hans MaassenSchumann, deceased Application ctober 3, 1951, Serial No. 249,540

14 Claims. (Cl. 181.S)

This invention relates to sound transmission and reproduction andparticularly to methods and apparatus utiliring multiplex selectivesympathetic resonance by what 1s termed herein a Macrophonic Unit.

The invention is based upon and incorporates a novel sound responsivematerial whose acoustic functioning is based on the phenomenon ofindividually selective sympathetic resonance to secure the completeproduction or reproduction of complex sounds to a degree never beforeattained.

Scientically, of course, the potentials of individual sympatheticvibration are well known, but in the practical field of sound, as forinstance in music, this knowledge is used only partially andincompletely, and almost incidentally, and in the most rudimentary andprimitive fashion. Such abortive uses may be present, for instance, in amarimba. or like instrument, carrying tubes with an air column tuned tothe fundamental tone of the corresponding sounding piece of metal orwood; in drums with two parallel skins tuned to each other, and in apiano when the sustaining pedal is used. But in this latter case, evenin a perfectly tuned instrument, sympathetic resonance is badly hamperedby the tuning in tempered pitch of every piano. For all practicalpurposes, even these instruments are so far from utilizing selectivesympathetic resonance to the degree necessary for respouse to everyvibration in the multiplex thereof as to be unworthy of consideration asexamples of utilization of the principles stated.

In the large eld of electro-acoustic sound transmission the principle ofselective individual sympathetic resonance has not yet been used. Forinstance, in all known present day loud speaker systems, a number oftones, different in character, pitch, and volume are producedsimultaneously by a sounding body of general resonance with a more o-rless flat surface, as, for instance, by a paper cone. While, of course,such paper sheet is tri-dimensional, i. e., it must have some thickness,the dimension in thickness is so minute in contrast to its otherdimensions as for all practical purposes to have but two dimensions.Owing to the integrality and homogeneity of the paper cone differenttone vibrations are therefore bound to interfere physically with eachother to unpredictable degrees, and at least to such an extent that theproduced sound is one which is possessed of a recognizable typicalcharacter of the particular sounding instrument, i. e. the typical loudspeaker sound.

Any sound, simple or complex, received microacoustically at its sourceby a microphone remains unaltered in its conversion with electricpulsations in the electrical transmission, and should be reproducedmacroacoustically, i. e. in amplified form as an exact replica of anyoriginal sound present in the conversion thereof into electricalpulsations, without any noticeable changes in character and qualityhappening in the amplifying unit. It is notorious of typical conespeakersvthat such macrophonic amplication is impossible and thedifferences berice tween the original sound and the reproduced sound areso evident, even in so-called high delity speakers, with multiple cones,etc., that anyone can determine instantly that the reproduction is of amodified character typical of such speakers.

In order to eliminate such acoustic distortions and changes in characterand quality of the reproduced sounds, the physical interferences betweenvibrations must be eliminated. As such interferences are inherent insolid, even, uniform and homogeneous Vibrating bodies, such as in papercones, this vibratory responsive unit must be replaced or augmented by avibration responsive unit in which mutual interferences aresubstantially impossible, if acoustic distortion is to be eliminated.

lt is a primary object of this invention to provide a vibrating body ofa heterogeneous three-dimensional structure containing a multiplicity ofvarigated vibroreactive units or items functioning in selectiveindividual sympathetic resonance without mutual interference.

It is a further object of the invention to provide a vibro-responsiveunit for functioning in selective individual sympathetic resonanceWithout mutua-l interference by which by-noises are better responded toand transmitted. By this means clearly audible and well balancedreproduction of very high pitched overtones and formants as well asacoustically complex mechanical by-noises, which represent to a largeextent the individual character of an original sound, such as music, aretransmitted. For instance, line by-noises produced by the scratching ofthe resined how on the strings of a violin, the air noise at the onblo-wof wood instruments and organ pipes, the impact sound of a piano hammer,and breathing by-noises in singing and speech, are all inadequatelyreproduced by a vibrating unit of a non-heterogeneous structureproducing simultaneously lower and higher pitched sounds. This losseffects a lack of naturalness in the sound of the individual instrumentsand consequently results in a lack of transparency in very complexmusical sound combinations noticeable especially in a reproduction of anorchestral piece.

ln carrying out the invention in an illustrative embodiment, l provideas a vibrating unit, either a natural or synthetic multiplex structurecontaining a great variety of vibroreactive particles or minute areasdisposed for simultaneous respective functioning in effecting the variedindividual sympathetic resonance combining in -a complex soundtransmission according to the improved method of lthis invention. Themultiplex structure, if a natural product, preferably will be treatedchemically, and the synthetic multiplex structure will usually, althoughnot necessarily, incorporate the chemical treatment in its formation tothe end that the particles or minute areas, which may be more or lessdiscrete, or continuations of other areas, having free or 4attachedends, combine elasticity with adequate body 4and tensioncharacteristics, for respectively producing a certain individual soundor vibratory resonance response according to their individualstructures, as determined by the weight, diameter, length and tensionthereof.

As purely illustrative examples of such structures occurring in nature,constituting raw materials possessing,y desirable multiplex structures,reference is made to certain types of natural Sponges and to thepericarpial skeletons of some gourd plants.

The synthetic structures, simulating in some stages of ytheir creationand organization the natural multiplex structures of the naturalmaterials mentioned, or otherwise formed by extrusions, moldings, andshapings and the like, may be produced with plastics i. e. thermoplasticor thermosetting resins land the like, rubber, natural or synthetic,cellulose of many types as of wood pulp, cotton, Wool, or asbestos,glass and other suitable raw material.

In order to give an example of the suitable treatment of natural grownraw material for purposes of this invention, it will be considered fromthe standpoint of using a natural product such as lulfa, in itstreatment and use in sound production or reproduction, for instance, atthe end of an electro acoustic sound transmission. The formation and useof synthetic materials for the purpose will follow the principles of thestructural entity of the lulfa as treated, so far as is possible withinthe limitations of the material itself, or will have its ownskeletonized mult-iplex structure, `which is readily accomplished whenthe operations of the unit are comprehended from the illustrative luft'ato be described.

They raw lua pericarp, on the market -in at, cornpressed pieces of Liqaegypzaca or Luya cylindrca, is placed in a bath of water or in a watersolution, say, with vinegar, in which it expands fully to its origin-alshape by its strong power of imbibition. After removing surplus liquid,the pericarp is cut open longitudinally and the inner vascular bundlesare `separated and cut as much as needed.

In a semi-dry state of the pericarp, or parts of it, are flattened outand fastened to a fiat piece of dry, solid material, such as a thickpiece of cardboard. In this res-trained position the luffa is thoroughlydried, say, under heat lamps. When completely dry, the lulfa is removedfrom the board and is cut and yshaped as suited for the differentadaptations to be later discussed. In order -t-o improve the -elasticityof the tissues and at the same time for protection `aga-inst airmoisture, the dried cut pieces are preferably, although not alwaysessentially, sprayed with a light texture of a Very liquid emulsion orsolution of natural or synthetic rubber or a plastic with similareffects. When this light coating dries it will be seen that the randomlengths, thicknesses, doubly or singly attached skeletal elements arepermanently fixed into a unitary but multiplex structure in which anycomplex sound finds some sympathetically responsive separatelyvibratable element or area having a natural period or frequency torespond by sympathetic resonance thereto, whether an isolated, or evencomplex or compounded vibration, and substantially Without mutualinterference With any other isolated or complex or compounded vibration.

It will be seen that as thus created, the structural unit has extremelywide uses in acoustic devices, Whether as comprising sounding orresonance boards for instruments, or as aiding devices for standardsounding boards or the like. However, -there is such a Wide field of usefor the invention in the art of speakers that it will be explainedillustratively in its association with or as replacements for typicalpaper cone speaker assemblies. It will be recognized, however, that inits broader aspects 'the impulse for acoustic reaction in selectivesympathetic resonance can be obtained in many d-ilferent ways.

In `the accompanying drawings forming part of this description:

Fig. l represents a fragmentary enlarged perspective of a multiplexstructural unit possessed of individual select-ive sympatheticresonance, and especially one of the natural forms thereof, such asluffa.

Fig. 2 represents a diagrammatic section through a speaker organizationin which vascular bundles of the illustrative treated and coated lufta,or its synthetic equivalent, are fixed rmly to the front side of a papercone speaker, generally conforming to the contour of the cone andconverging toward an apertured center concentric with the focal axis ofthe cone. The direction of propagated sound is indicated by the arrow.

Fig. 3 represents a similar section through another speaker organizationin which a diaphragm of treated lula, or its synthetic equivalent in aseries of vascular bundles is provided, generally flattened on one sideand fixed over the metal frame of the loudspeaker. This diaphragm iscontacted in its center acoustically by a luffa bundle cut for thepurpose and contacting directly with the moving coil unit mounted on oractuating the apex of the paper cone, and functioning as a sound bridgefor transmitting vibrations directly into the lula diaphragm for thesame purpose and with function related to the sounding post of a violin.The direction of propagated sound is indicated by the arrow.

Fig. 4 represents a similar section through a flat diaphragm of thin,airproof and elastic material, illustratively rubberized, thin nylon,carrying over its entire surface a number of treated vascular bundles oflutfa or its equivalent, cemented to lthe flexible diaphragm as withlatex, `and disposed as a vibra-tory unit in airtight reation to themetal frame of the speaker, and with a supplemental or auxiliarypreferably parabolic reflector disposed in juxtposition to the vibratoryunit for rellecting the sound for transmission in the directionindicated by the arrows.

Fig. 5 represents a diagrammatic elevation of the organization of Fig.4, incorporating a sound shade closed by a diaphragm with the entrappedair heated by a heat lamp, to improve the acoustical quality.

Fig. 6 represents digramma-tically a switching circuit combining aspeaker according to this invention in alternation to or insupplementation of a conventional cone speaker, controllable through a`rheosta't for modulating or cutting out the cone output.

Fig. 7 represents a fragmentary section through ia sounding boardcarrying a plurality of bundles of the heterogeneous vibrating material,such as lul-fa.

Referring to the fragment shown in Fig. l, the luffa pericarp comprisesvascular bundles comprising pluralities of main branches 10, and submainbranches 11, generally parallel to the primary main branches, and myriadcross connections 12 extending between the main branches. These crossconnections and various main branches meet in nodes of varying sizes,the branches and cross connections are of almost infinite ranges inthickness, length, tensions, and other characteristics, and are in moreor less random directions of relative extent and angularities and whensevered to form cut bundles, this random character of the variouscomponents enhances the range of acoustically responsive individualcomponents, in the organization ofthe heterogeneous vibratory unit.

In utilizing such a heterogeneous organization, in one speakerorganization as indicated in Fig. 2, the speaker organization initiallycomprises a paper cone i4, attached to and vibrated by the magnetic coilorganization 15, in any conventional hook-up therewith, so thatelectrical impulses, carrying all of the various vibrations of thesource, effective on the electrical unit 15, transmit them to cone 14.As noted, owing to the homogeneous texture of cone 14, mutualinterferences occur, damping and distorting certain vibrations, when thecone is used alone. However, a mass of the vascular bundles of treatedlulTa 16, or the like heterogeneous mass, are xed firmly to the frontside of the paper cone, and provided preferably with a central aperture17, concentric with the coil unit 15. In use the vibration of theloudspeaker cone 14 is purposely suppressed and is replaced by thevibrations in the luffa bundles. This is done for the purpose ofstressing acoustically the individualization in a compound sound by amultitude of individual sympathetic reactions in the vibrating unit.

In the form of invention shown in Fig. 3. the paper cone 20 is provided,mounted on annular frame 26 and actuated as usual by the magnetic coil22 connected to its apex. A hollow cylinder 23 is provided substantiallyconcentric with which a luffa-made sound bridge element 24 and ismounted in contact with the vibrating element of magnetic coil 22.Vascular bundles of luffa are mounted as a luia diaphragm 21 on framemember 26 in contact in the center With the bridge component o1 element24. When the magnet coil 22 is energized with sound energy components,the full sound of the paper cone is unhampered. This is rstly due to thecomplete porosity of the diaphragm 21, and secondly due to the extremelightness in weight of the luEa-made sound bridge 24. At the same time,by the individual sympathetic resonance of an added multitude ofstructurally diierent vibrating particles 25, the improved identity withthe original sound becomes clearly discernible.

in the form of the device shown in Fig. 4, the paper cone 3d is mountedwith a magnetic coil organization 3i at its apex on frame 34 of theloudspeaker. An elastic diaphragm 32, as of rubberized or latex-coatednylon, is stretched on frame 34 of the speaker unit, and carries on oneface a luffa diaphragm 33 mounting a plurality of vascular bundles ofluia 3S. A parabolic sound reiiector 36 is provided in iixed, butadjustable, relation to the frame member 34 of the speaker organization.Reector 36 may be nonparabolic, if desired.

When magnet coil 31 is actuated, the cone 30 vibrates an air columnexisting between diaphragm 32 and front of cone 3i?, and the sound borneby this air column is almost entirely replaced by the much clearer andmore complex sound reproduction by the vascular bundles 35 on thediaphragm 33, reacting acoustically to the vibrations of the closed-inair column. At the same time, the sound coming from the rear of the coneremains unhampered. ln `order to exploit the full extent of theacoustical quality of this combination, the loud speaker unit describedis placed in front of the preferably parabolic sound reector 36,adjacent the group of luifa bundles on the diaphragm. Preferably, theexternal surfaces of the luifa bundles arc shaped to conform to therounded surface form of the reflector.

In order to raise the temperature of the air surrounding the macrophoneset-up of Fig. 4, advantageous for any development of sound, a soundshade 37 can be added to the edge of the preferably parabolic soundreflector, closed by a diaphragm 38 of thin elastic material, as, forinstance, rubberized, thin nylon. This diaphragm allows a highertemperature inside the sound shade, produced by a suitably placed, smallheat lamp 40, without interfering with the outcoming sound, as shownschematically in Fig. S. The thin, rubberized nylon diaphragm isimpervious and prevents the escape of the heated air, while permittingfree passage of sound waves. The parabolic reflector aids in effectivelyfocussing the heat energy toward the center of the speaker, withenhanced etliciency of the macrophonic unit. Obviously, the lamp may bewithin the enclosure and at any desired point therein.

in Fig. 6 a speaker, as shown in any of Figs. 2, 3, or 4, indicatedgenerally at 41, has its magnetic coil coupled to a source of electricalenergy containing converted sound energy. A conventional loudspeaker 42is provided in reasonably close association therewith, and this iscoupled in parallel relation to the electrical energy source through arheostat 43. By judicious use of rheostat 43 a mixture of sounds iscreated from the respective speakers, which in combination giveexcellent sound effects, capable of modulation as desired. Use of therheostat or potentiometer d3 is controlled in accordance with the amountof space or room in which the sound is reproduced, as the standard conespeaker only provides a background of room effect.

in each case, preferably, the vascular bundle for a vibrating group ischosen from luffa pericarps, or the simulations thereof, natural orsynthetic, differing in size, in order to improve the structural varietyof vibrating items in the combined group.

it is usually preferred that the electric volume be raised somewhat overthat necessary with ordinary paper cones, in proportion to the enlargedamount of vibrating material.

it wiil be appreciated that the selection of a given form of unit of thethree types shown in Figs. 2, 3, and 4 and 5 respectively, alone or in acombination as shown in Fig. 6,

6 depends upon the purpose of the sound apparatus and the amount andkind of space into which the reproduced sound is to be projected, whichpurpose and space considerations differ widely over a large iield ofsound reproduction.

The invention effects remarkable improvements at the end of anelectro-acoustic sound transmission for the reproduction of music,speech, or other sounds, as described. It is repeated, however, that ithas wider applications than in these speaker installations, and that thauction of units of the invention reacting in multiplex selectiveresonance in sympathetic vibration offers to the builder of musicalinstruments a very delicate sound amplification, for instance, inconnection with the functioning of the body of a violin or the thinsounding board or" delicate keyboard instruments like the harpsichord orclavichord. A detail of such sounding board or body is shown in Fig. 7,in which a relatively thin sounding board 5t) to which bundles of luifapericarp 51 are attached, is shown.

When music is transmitted by a sounding unit of heterogeneous structureas recited herein, the sounds, diiferent in pitch and volume andreproduced by items, areas, or particles vibrating in selectivesympathetic resonance occur in ditferent places all over the unit. Thusa wandering about of the sound vibrations can be clearly followed by thesense of feeling, for instance, by touching the surface of the soundingunit with the full palm of a hand. Thus, as an interesting sidelight onthe invention, a deaf person is enabled by the invention to enjoy musicby touch, in a fashion similar, though more direct and more complex, tothat by which a blind man can enjoy a story printed in Braille.

lt is pointed out again that although natural luifa has been recited aspreferred form of heterogeneous vibration-responsive material for thepurpose ot securing individual selective sympathetic resonance, it isillustrative of a larger group of materials, which are available and arecontemplated for use herein.

Having thus described my invention, l claim:

l. A resonating unit of heterogeneous structure containing a manifoldquantity of individual vibro-responsive components, each componenthaving its own specific combination of length, weight, thickness andtension characteristics and being sympathetically resonant to aparticular frequency of vibration in the audible range, said componentsbeing of such great number and of such variegated resonance response byreason of relative differences in such combinations of characteristicsthat there is a resonating component in the unit for substantially everyvibration in the audible range, whereby substantially all of thevibrations of a complex of sounds in the audible range incident on saidunit are resonated and propogated substantially without mutualinterference, and means for transmitting complex sounds to said unit.

2. A sound producing organization comprising a heterogeneous structureformed of an integral member containing a multiplicity of vibro-reactivecomponents, having random combinations of length, Weight, diameter andtension characteristics susceptible to individual and selective variedsympathetic resonance, and means for impressing a complex sound on saidstructure whereby without mutual interference in said structure theindividual vibrations in the complex are resonated in said structure.

3. An organization as recited in claim l in which said means comprises asounding board.

4. An organization as recited in claim l, in which said means comprisethe magnetic output of an electroacoustic sound transmission.

5. An organization as recited in claim l, in which said means comprisesa cone speaker.

6. An organization as recited in claim 2 in which the structurecomprises pericarps of luifa for producing si- 7 multaneously a varietyof sounds dilerent in pitch and character by individual sympatheticreaction.

7. An organization as recited in claim in which the structure comprisesdried pericarps of luia for producing simultaneously a variety of soundsdifferent in pitch and character by individual sympathetic reaction, anda thin layer of latex-like coating on the pericarp, of such thinness asto inappreciably aiect the elasticity of the lutfa material Whileinsulating the components against moisture penetration.

8. An organization as recited in claim 5 in Ywhich the structure is atthe end of an electro-acoustic system for sound transmission andcomprises vascular bundles of luta.

9. An organization as recited in claim 2 in which the structurecomprises vascular bundles of lua and a separate vibrating part ofhomogeneous structure.

10. An organization as recited in claim 1, in which the structurecomprises vascular bundles of lula formed as a diaphragm.

11. An'organization as recited in claim 1 in which the structurecomprises vascular bundles of lutia formed as a diaphragm, a magneticvibratory element, and a lutfa bridge contacting the vibratory elementand said diaphragm to transmit vibrations to said diaphragm.

12. An organization as recited in claim 2, in which the organizationcomprises a exible and elastic diaphragm formed of woven fabric coatedwith latex, vascular bundles of luffa mounted on said diaphragm, andmeans for vibrating said diaphragm with a complex of vibrations to whichthe lulfa responds in selective sympathetic vibration.

13. An organization as recited in claim 2 in which the structurecomprises a tlexible and elastic diaphragm,

vascular bundles of lutfa mounted on said diaphragm, means defining withsaid diaphragm an air column for vibrating said diaphragm, and means forenergizing the air column with vibrations.

14. A resonating unit of heterogeneous structure comprised of aplurality of generally longitudinally extending irregularly spaced mainbranches, and a myriad of connections of which some are connected to andextend between pairs of main branches and some are connected to andextend from one main branch, each connection having its own combinationof length, Weight, thickness and tension characteristics and beingsympathetically rcs Onant to a particular vibration in the audiblerange, said connections being of such great number and of suchvariegated respective combinations of such characteristics and ot'respective sympathetic resonance response that there is a resonatingconnection in the unit for substantiallyl every vibration in the audiblerange, whereby substantially all of the vibrations in a complex ofsounds in the audible range incident on said unit are rcsonated.

References Cited in the le of this patent UNITED STATES PATENTS Re.16,367 Valentine June 22, 1926 1,812,389 Wente lune 30, 1931 1,851,208Nicolson Mar. 29, 1932 2,013,695 Nicolson Sept. 10, 1935 2,670,053 DomsFeb. 23, 1954 FOREIGN PATENTS 279,180 Italy Nov. 5, 1930 746,599 France.Tune 1, 1933 494,696 Great Britain Oct. 31, i938 510,707 Great BritainAug. 4, 1939

